The Hewitt-Sperry Automatic Airplane was a project undertaken during World War I to develop a flying bomb, or pilotless aircraft capable of carrying explosives to its target. It is considered by some to be a precursor of the cruise missile.
Conceptual development
Before World War I, the possibility of using radio to control aircraft intrigued many inventors. One of these, Elmer Sperry, succeeded in arousing the US Navy's interest. Sperry had been perfecting gyroscopes for naval use since 1896 and established the Sperry Gyroscope Company in 1910. In 1911, airplanes had only been flying for eight years, and yet Sperry became intrigued with the concept of applying radio control to them. He realized that for radio control to be effective, automatic stabilization would be essential, so he decided to adapt his naval gyro-stabilizers (which he had developed for destroyers).
In 1913, the Navy provided a flying boat to test and evaluate the gyro-based autopilot. Sperry's son Lawrence served as an engineer during the test phase. In 1914, Lawrence Sperry was in Europe and observed the developing techniques of aerial warfare, including the use of aircraft. In 1915, the New-York Tribune broke the news of the project. In 1916, the two Sperrys joined Peter Hewitt, an early inventor of radio-related devices, to develop an explosive-laden pilotless airplane.
Elmer Sperry and Hewitt served together on the Naval Consulting Board, where they both were members of the Committee on Aeronautics and Aeronautical Motors. Because of these connections, they were able to arrange for a representative of the Navy's Bureau of Ordnance, Lt. T. S. Wilkinson, to examine the control equipment they assembled. The system consisted of a gyroscopic stabilizer, a directive gyroscope, an aneroid barometer to regulate height, servo-motors for control of rudders and ailerons, and a device for distance gearing. These all could be installed in an airplane which could be catapulted or flown from the water, and would climb to a predetermined altitude, fly a pre-set course, and after traveling a pre-set distance, drop its bombs or dive to the ground. Wilkinson reported that the weapon did not possess a degree of accuracy sufficient to hit a ship, but, because of its range of , it might be of interest to the Army.
Construction
However, after the US declaration of war on Germany, Sperry began urging the Navy to revisit the idea. The Naval Consulting Board supported him, and formally requested the Secretary of Navy to apportion $50,000 for the work. The government thus included the development of the flying bomb or aerial torpedo in its war preparations. The Senate went so far as to establish two classes for the type weapon, one for wireless control, the other for completely automatic operation. Final approval came on May 17, 1917, and the Navy agreed to provide five (later upped to seven) Curtiss N-9 seaplanes and to purchase six sets of the Sperry automatic control gear. Navy Secretary Josephus Daniels agreed to spend $200,000 on the project, with the money to be administered by the Bureau of Ordnance, the Bureau of Construction and Repair and the Bureau of Engineering. The operation was established at Copiague, Long Island.
The autopilot equipment was already designed, but the radio control system hadn't been fully developed, so while the hangars were being built at Copiague, Sperry turned his attention to this aspect, purchasing rights to a number of patented radio-related inventions. Ultimately, though, the radio control systems were not used on the Hewitt-Sperry Automatic Airplane. Later, in 1922, the system was installed on several Verville-designed planes along with gear for the Army Air Services engineering division. These aircraft successfully hit their targets from ranges of 30, 60 and .
Flight test
The first test flights of an autopilot-equipped aircraft was in September, 1917, and took place with a human pilot on board to fly the takeoff. By November, the system successfully flew the aircraft to its intended target at a range, where the distance-measuring gear would drop a bag of sand. Accuracy was within two miles (3 km) of target.